Where Does It Hurt?

One of the most frustrating aspects of diagnosing and treating lameness in horses is that they can't tell you where it hurts. But a relatively new technology to the equine world is helping some veterinarians pinpoint lameness problems. Bruce Lyle, DVM, a veterinarian who focuses on foot care in Aubrey, Texas, has been using a Matscan pressure measurement system from Tekscan in his clinic for about nine months now, and he finds it to be a very useful tool.

While an assistant walks a horse over the 28x60-inch mat (the largest of these mats currently in use in clinical practice in the U.S.according to Tekscan; the only other one is at Rood and Riddle Equine Hospital in Kentucky), Lyle records pressure measurements on his computer. The resulting video shows the varying pressures of the hoof on the mat as different colors, much like a weather map uses color to show varying intensities of storm activity, and graphs the force over time. Coupled with physical examination and radiography, this information helps Lyle identify what structures might be subjected to more than their fair share of pressure, torque, or strain. He can then decide how to change the forces at play to optimize the healing environment, and in many cases alter high-risk or currently painful areas to gain a sounder horse.

Matscan Lameness Evaluation

When a horse is evaluated, he simply walks across the mat, which is connected to a computer via a USB cable. The computer records pressure measurements 40 times per second. See this horse's mat evaluation video

Dr. Lyle's Case Descriptions

Follow along as Dr. Bruce Lyle explains his evaluation and treatment of two cases using the Matscan system.

"This system provides an awful lot of information that helps you help that horse," he explains. "It allows a mechanical analysis of the landing load and breakover pattern of that foot and leg, and can clarify a lot of things you might see on a radiograph (X ray), sonogram, or MRI image. Like good radiographs, it provides all parties involved with objective data from which to work. For example, everyone can see clearly that a horse's ground contact begins with the lateral toe, moves slightly to the center of the foot during peak stance load, and then breaks over the lateral toe. So now we can create a trim or trim/shoe program to change (balance) those forces, and then we can see if we've accomplished what we set out to do.

"That was one of the things that interested me when I saw (this system) demonstrated on the human side," he adds. "They tape you walking or swinging a bat, club, or whatever, and use the mapping system to identify problem areas and custom-design orthotics for you. That's exactly what we're doing for horses."

A Few Lessons Learned

Biomechanics The Matscan information has taught Lyle quite a few things, he says, such as the importance of the foot's center of force relative to not only the foot but also the rest of the limb. "It may not always be where you think it is," he comments. "Forty frames of information per second via this technology are better than my eye!"

He notes that moving the center of force to the back of the foot without decreasing the palmar angle (the angle the wings of the coffin bone make with the ground) can relieve a lot of problems. "Toe-first contact can be a killer, and if the center of force stays forward during the stance phase, the structures in the back of the foot can experience an awful lot of torque and strain," Lyle explains. "One way to relieve this is to move breakover (the forwardmost ground contact point of the foot) by reducing the toe wall length. Depending on the foot mass present as viewed on radiographs, this can be done via the trim, or if the foot is short and shallow already, shoe design and manipulation can accommodate the mechanics needed."

Laminitis "Probably one of the #1 things to do in an actively laminitic horse is to unload the wall," he comments. "Laminitis is probably the simplest problem I deal with on the mat because you already know the fundamental problem is the interface between the hoof wall and dermal/bone structures, so if you can relieve the ground reaction forces on the wall, you have relieved what's stressing those laminar tissues. When you unload the wall they do so much better; it's so simple but so difficult to see any other way."

"Several cases that have come to me with 'sole support' have actually had none (because the sole showed no weight bearing on the Matscan), and then the trick becomes not creating focally intense spots of sole pressure that perpetuate pain via bruising and abscessation," he adds. "There’s a very delicate balancing act you have to see to believe!"

Tenotomy management "The mat has helped us minimize focal loading/pressure spots in post-op tenotomy horses, much like the technology is used in people to relieve pressure spots for diabetic pressure ulcers," Lyle explains. "That's been huge in some cases, and we couldn't perceive that (see those pressure spots) with radiographs or physical examination."

Effects of shoeing interval "The dynamics of the foot and its forces change on a week-to-week basis during the growth cycle," he states. "With some horses, that's all the window (of soundness) they have, so that's why they have to be trimmed/shod very specifically and regularly."

Do these findings on concrete apply to soft ground too? Lyle answers: "The forces will change some on soft ground vs. the concrete we're using, but the lowest (most loaded) spot on the foot will still be the same. It's just that soft ground will accommodate it more. Force is lessened, but the load tendency is still in the same direction. And soft ground can actually exacerbate some conditions and loading patterns, which we can deduce and hopefully correct with the combination of radiographs and matscan analysis."

What's Next?

Lyle says he'd like to be able to use this technology on horses at different gaits. "We have trotted a few horses across the mat, and their landing load and breakover patterns were almost identical to those at the walk," he reports. "But it would be great to compare patterns at the canter and gallop. If we could coordinate those gaits with video, we could probably do some things from the bottom up to help upper limb lamenesses.

"Beyond that, I'd love to continue to look at therapeutic interventions and their effects on long-term results," he adds. "And I think we could investigate shoe and pad materials to find ones that are best suited to different problems on patients with different weight and gait characteristics."

While Matscan is a valuable tool, Lyle notes that it's just that--one tool in a veterinarian's arsenal. "There's never going to be one isolated test that will provide an answer for all lameness cases," he summarizes. "That's the art of doctoring; we take all the science from ground reaction forces to MRI to pathology and physiology, and the art of interpreting that to develop a diagnosis and treatment plan is what constitutes medicine."

Tekscan has been making pressure measurement systems for various applications since 1987, and currently offers the Matscan as well as hoof and saddle pressure measurement systems for equine use. For more information, see www.tekscan.com.